ENSC 408: Lab 3 Tephigrams September 23, 2019 Low Temp. (C) High Temp. (C) (no/yes/type) Observed 7 17 0 Forecasted 6 16 0 Class Average 7 17 1 Class 6 17 0 7 16 1 7 16 1 8 17 1 6 18 1 5 16 1 4 19 1 Results

Average Score: 6 / 10 Isobars (kPa) Mixing Ratio (rs)

Tephigrams

Objective: • To learn techniques to study vertical atmospheric structure using a tephigram Materials: 1. A blank tephigram 2. Coloured pens/pencils

Dry Adiabat (θ) Isotherms (T)

Moist Adiabat (θw) Plotting on a Tephigram

For the first part of the lab you will be plotting radiosonde data on your tephigram copy 1. Add points for and Dewpoint Temperature at each level 2. Connect points with a straight line for each field T 3. Identify each line as ‘T’ and d T ‘Td’ 4. You will also add a wet-bulb temperature (Tw) line in a later question (#7) in a different colour Pressure (kPa) T (C) Td (C) Then there are 14 questions to 100 25 10 answer (Questions 2 – 15 in your 90 25 15 lab manual) 70 6 4 Stability of Vertical Levels

Levels can be: • Stable • Unstable • Conditionally unstable • Neutral Determined by comparing the slope of the ELR with that for the dry and moist adiabats Identification of Tropopause, Isothermal Layers, and Temp. Inversions

Tropopause • The boundary between the troposphere and stratosphere • Identified as an inflection point in the sounding where the ELR decreases to 2 C/km or less – usually near 20 kPa in mid- latitudes Isothermal Layers • Layers of constant temperature • Slope of ELR = Slope of Isotherms Temp. Inversions • Layers which warm with height • Slope of ELR > Slope of Isotherms

Source: Stull, R (2017) Lifting Condensation Level (LCL)

Lifting Condensation Level (LCL) • The pressure level at which a parcel, when lifted adiabatically, becomes saturated (typically the base) • Determined by joining a line from the surface temperature, parallel to the dry adiabat, with a line from the surface dewpoint temperature, parallel to the isohumes. The LCL is located at the confluence of the two lines.

Source: https://weathertogether.net/weather-101/how-to-read-skew-t-charts/ Level of Free (LFC)

Level of Free Convection (LFC) • The pressure level at which a parcel of air, lifted adiabatically, first becomes warmer than its surroundings in a conditionally unstable atmosphere • Determined by drawing a line from the LCL, parallel to the moist adiabat. The LFC is located at the intersection of this line and the ELR

Source: https://weathertogether.net/weather-101/how-to-read-skew-t-charts/ Amount of Water Condensed in a Parcel Lift

Amount of Water Condensed in a Parcel Lift • Determined by subtracting the mixing ration at the top of the parcel lift from that for the bottom In this example:

• rT – rnew = 2 g/kg – 0.18 g/kg = 1.82 g/kg

Source: Stull, R 2017 Latent Instability

Latent Instability • if a parcel somewhere along the profile can be lifted so that it eventually reaches a (LFC) where it is warmer than its environment and therefore buoyant. • A vertical zone of latent instability can be identified on a tephigram by tracing the coldest moist adiabat line that cuts the temperature profile, to the ground. • Zones where this line is cooler than the wet bulb profile, are zones of latent instability. Source: https://slideplayer.com/slide/4348000/ Potential Instability

Potential Instability • If a portion of the profile has a wet bulb which decreases with height, then lifting this vertical zone will eventually lead to an unstable profile. • Zones of potential instability will have a wet bulb potential temperature profile that decreases with height • Slope of wet bulb temperature < Slope of moist

adiabats Source: http://tornado.sfsu.edu/geosciences/classes/m201/buoyancy/SkewTMastery/mesoprim/skewt/stability_potential5.htm Convective Condensation Level (CCL)

Convective Condensation Level (CCL) • The level at which a parcel of air becomes saturated when lifted adiabatically • Identified as the intersection of the temperature curve with a line drawn from the average mixing ratio of the surface layer (bottom ~5kPa, parallel to the isohumes

Source: http://kejian1.cmatc.cn/vod/comet/mesoprim/tephigram/media_gallery.php.htm (Tc)

Convective Temperature (Tc) • lowest temperature to which the surface air temperature must be heated before a parcel can rise dry-adiabatically to its LCL without ever being colder than its environment • Determined by drawing a line from the CCL to the surface, parallel to the dry adiabat

Source: http://kejian1.cmatc.cn/vod/comet/mesoprim/tephigram/print_2.php.htm Discussion Questions

In addition to the annotated tephigram, there are several questions to answer • Questions 2 – 5, 7 (at the end!), and 12 – 15 will require additional write-up • Some may be able to be included on the tephigram instead if desired! • The remaining questions can be answered on the tephigram plot • Please indicate in your write up that the answer is located on the tephigram plot if so Assignment

This lab assignment is due at the start of next week’s lab (October 1st at 8:30 am) It is worth 4 % of the final course grade Includes the annotated Tephigram with: 1. Temperature (#1), dewpoint temperature (#1), and wet bulb temperature (#7) 2. Layer stabilities (stable, unstable, etc) (#6) 3. Additional annotations (can also be submitted with discussion questions) • Tropopause, CCL, etc As well as a write-up of the remaining discussion questions